The Yeltz were due to face Concord Rangers over two legs for a place in the Wembley final, but have now been left in limbo after the FA announced the suspension of the competition.
The club sold more than 3,000 tickets for tomorrow’s scheduled first leg at The Grove and were due to travel to Essex for the return leg on March 28.
McKenna, who took over the club with Karen Brookes in October 2018, said: “As a club we are absolutely devastated, and I’m gutted for all the fans who were looking forward to it.
“We are trying to remain positive, and first and foremost you have to think about people’s health and safety.
“These are remarkable circumstances and you have to have a common sense approach to dealing with it. There’s a lot of financial implications that we will have to deal with as a club, and from a football angle, considering the momentum we have got it is devastating.”
The Yeltz are fighting on two fronts this season, and currently sit second in the Southern Central Division with a game in hand.
They have nine games left and are due to host Didcot Town on March 24.
League bosses are due to make a decision on future fixtures after all matches were postponed last weekend.